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Short-range Magnetic Ordering in the Geometrically Frustrated Layered Compound YBaCo4O7 with an Extended Kagomé Structure

Structural and magnetic properties of the geometrically frustrated layered compound YBaCo4O7 have been studied by magnetization and neutron diffraction. A layered type crystal structure, with alternating tetrahedral layers of Kagomé and triangular types, along the c axis (hexagonal symmetry, space group P63mc) has been found. The oxygen content of the present compound was determined by iodometric titration to be 7.00{\pm}0.01. Presence of a short-range antiferromagnetic ordering (below TN ~ 110 K) has been concluded from the appearance of an addition broad magnetic peak (at Q ~ 1.35 Å-1) in the neutron diffraction pattern. A staggered chiral type (\sqrt{3}\mult \sqrt{3} ) spin structure in the Kagomé layers has been found. Presence of a significant magneto-structural coupling is concluded from the changes in lattice parameters across the magnetic ordering temperature TN ~ 110 K.